I've known some nuisances in my time!

But no, fining of landlords / property owners for failure to abate a nuisance was not uncommon around the time your Halpin/Conlan branch lived in Dublin.
Nuisance covered a wide spectrum of scenarios, but generally something related to sanitation / public health. For example, one of the stranger cases of Dublin nuisances at that time was tripe being left in a pile (to tenderise) for 5 days in the cellar of a residential property before being cut up for human consumption - needless to say, the local residents complained about the stench.
However, a great many 'ordinary' nuisances simply related to the properties and their environs. Defective drainage / sewage, yards and paths being soft mud rather than stoned / concreted, deposited rubbish, dangerous staircases, water ingress, general filth, that sort of thing. In a few worst cases, properties and alleyways were deemed so unfit for human habitation that the recommendation was to close and knock down.